Because of the many possible failures which may occur in a capacitor, the complete testing of capacitors has been a difficult task. However, the principal defects which occur in capacitors are change in capacitance, excessive leakage, breakdown at rated voltage, and dielectric absorption. These defects are most common in aluminum electrolytic capacitors because of the tendency for the dielectric material to dry out.
The most commonly used method for testing capacitors for these undesirable conditions involves the use of a bridge which can be used to measure capacitance and also to provide a dissipation factor. While such a measurement procedure may be suitable for laboratory use, it is too complicated and time consuming for use in trouble shooting electronic circuits such as television receivers, radios and the like.
Instruments for use in measuring capacitance by determining the time required for the capacitor to charge through a known resistance have been on the market, but they do not test for leakage, breakdown or dielectric absorption. However, these other defects are sufficiently common to warrant their consideration when trouble shooting circuits which include capacitors, and particularly aluminum electrolytic capacitors.